Answers to Your Questions About the Boeing 737 Max 8

Answers to Your Questions About the Boeing 737 Max 8

The Ethiopian Airlines plane that crashed Sunday, killing 157, was the same model that crashed in October during a Lion Air flight in Indonesia. The two deadly accidents raised questions and public alarm about the safety of the aircraft, a Boeing 737 Max 8.

More than 1,000 readers responded when we invited questions. Here is a selection, with answers from Christine Negroni, an aviation writer, a former air safety investigator and the author of the book “The Crash Detectives.”

Questions have been lightly edited for clarity. If you have more, please leave them in the comments.

Have any U.S. airlines grounded the Boeing 737 Max 8?

— Mark Donald, Dallas

American Airlines and Southwest Airlines, the only two United States carriers flying the Max 8, have both opted to keep the airplane in the air.

Which airlines have the Boeing 737 Max 8 in their fleet, and what’s the best resource to see what plane will be flying a particular route?

— Shehroz

Around the world, 47 airlines have the Max 8 in their fleet, including airlines on every inhabited continent. But more than two-thirds of the airlines operating the Max 8 have grounded it.

During online booking, travelers can see the model of the aircraft assigned to their flight when they select their seat. Several websites dedicated to frequent travelers also provide this information, including and Beware of canceling a ticket because you don’t want to fly on the Max 8. The airline probably won’t refund your money or let you rebook without a penalty.

Is the new technology associated with the Lion Air crash new to only the Max 8 series of aircraft? If it is found that the same technology also had a role in the Ethiopian Airlines crash, what sort of repercussions would Boeing be subject to?

— Marcus Bierbaum, Cleveland

The technology that is under scrutiny is the maneuvering characteristics augmentation system, or MCAS. It is part of the flight control software on both the Max 8 and the Max 9. If information from the Ethiopian Airlines crash suggests the software might have been a factor in the disaster, the consequences for Boeing could be severe. It has already begun a costly and complex redesign of the flight control software. It has been sued by families of the victims and suffered a blow to its reputation.

Boeing’s customers have also suffered consequences, as the majority of airlines that fly the Max 8 have grounded their planes or have been told to by their government’s regulators. Additionally, on Tuesday, the European Union and other countries around the world banned Max models from flying in their airspace.

What training is required for 737 pilots to transition to flying the 737 Max 8? Have the requirements changed?

— Don Griffin, Houston

The training required to transition from one model of 737 to the next depends on the airline. The 737 has a “common cockpit” design, meaning that a pilot certified to fly one model can easily move to another. Airlines that use several variants of the aircraft appreciate that flexibility.

A Southwest Airlines captain told me that at his company pilots who will fly the Max 8 are required to watch a video to familiarize themselves with slight differences in the systems and the engines. A spokesman at American Airlines, Ross Feinstein says pilots must review a training manual before moving to the Max.

Are all pilots that fly the 737 Max 8 explicitly trained on Boeing’s MCAS flight control system? Do they learn how it works and how to turn it off if it malfunctions?

— Alexandra Zaporozec, Chicago

Before the crash of Lion Air Flight 610 in October, Boeing had not notified pilots that the MCAS was operating on the Max or that in certain circumstances it might cause the airplane to pitch down. After the Lion Air crash, Boeing sent a service bulletin to its customers, and the Federal Aviation Administration followed up with an emergency directive ordering Boeing to change the airplane flight manual and provide the flight crew with a way to avoid being surprised or reacting incorrectly to the MCAS.

Have pilots on other flights of this plane experienced failure of the sensors and successfully manually overridden the MCAS?

— Jerry Engelbach, Mexico

The day before the Lion Air crash, the pilots who flew the same airplane reported problems with the angle-of-attack sensor, which tells pilots the angle of the airplane as it passes through the air. Maintenance workers at Lion Air replaced the sensor, and the plane was put back in service to fly as Flight 610. Outside of that event, which was revealed after the crash, there have been no other public reports of pilots experiencing this kind of problem.

That said, pilots of any version of the 737 could encounter situations in which a flight control surface on the tail of the airplane can push the nose down unexpectedly, causing the plane to dive. This is a situation they train for in the simulator.

What they could not train for — because they did not know — was that the MCAS would force the airplane into a cycle of repeated dives. The pilot could stop this cycle only by removing power from a control surface.

Can airlines or pilots opt to permanently disable the MCAS software feature?

— Christoph Dwertmann, Sydney, Australia

That does not appear to be an option. Keep in mind also that changing software is not as easy as swapping digits. Boeing needs to be quite sure that by fixing a known hazard it doesn’t insert an unknown hazard.

I’ve heard one report of an eyewitness who saw smoke emanating from the Ethiopian plane just before the crash. Is it confirmed that fire was observed from the tail section before impact?

— Jim Pollock, Boulder, Colo.

There has been no confirmation of a fire on board the aircraft before the accident, but certainly everything that happened on the airplane before its impact will be part of the investigation. Evidence of a fire would be recorded by the flight data recorder, which is already in the custody of air safety officials. The flight data recorder and the cockpit voice recorder, known together as black boxes, provide voluminous information about the airplane, its engines and its operation.

Regarding the co-pilot, did he have only 200 total hours of flying ever?

— Melissa Strong, New Orleans

The chairman of Ethiopian Airlines said the co-pilot, Ahmed Nur Mohammod Nur, had 200 hours. Those hours were most likely in addition to the time he had spent learning to fly. According to Yeshiwas Zeggeye, a flight instructor with the airline, pilot cadets accrue 200 or more hours during their training.

How does the safety record of the 737 Max 8 compare with that of Boeing’s other jets?

— Lauren Ammerman, Texas

Gauging the safety of a particular model of airplane is a tricky business. On what criteria is “safety” based? Accidents? Only fatal accidents? What about near accidents or events that surprise the pilots? An airplane may not crash but still hold unrecognized hazards. And an airline may not have good maintenance practices.

To identify safety issues, investigators around the world are turning to big data, examining volumes of information generated on hundreds of thousands of ordinary flights to try to determine if planes and pilots are operating as expected and identify when they are not. This is considered a more effective way of detecting hazards than learning about them from disasters.

How closely related, in design of flight controls and flight software, are other 737 Max models? Could a possible grounding of the 737 Max 8 fleet also affect other Max models, such as the Max 9?

— Fabian Grusdt, Munich

Both the Max 8 and the Max 9 have the MCAS system, and the Max 9 has also been targeted for grounding in several countries.

Is there any reason to believe foul play may have been involved in this crash?

— Rick Thompson, Sanibel, Fla.

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